Don't you leave your boxes up through the summer Boco? I bet the bears love the beaver board boxes.
I use whatever is cheap and handy, have some plywood ones, out of various thickness of leftover and scrap plywood. And I have a bunch made out of 1" pine and fire boards, have a friend whose dad owns a sawmill and I get the ends from when he saws boards out of logs and then cuts them to length, or some bad chunks with wane on them, etc. Those boxes are heavy, especially after they soak up water, but they are free and work good.
over all my traplines I must have 300 boxes out(not all set each year)I rarely have problems with bears wrecking boxes.
The squirrells used to chew on the old plywood,but they must not like the glue in the new plywood they dont eat them much.
I went into a part of my trapline a few years ago that I hadnt been into in about 20 years-found some old boxes half grown into some trees.
I have lost more boxes to blowdowns than bears over the years.And we are polluted with bears here.
Some guys seem to have problems with bears,It may be from lure use.I dont trap until well into freeze up,except for a few boxes if I'm setting for mink and I use bait only(frozen) and I remove all the bait when trapping is done end of feb.Bears dont come out here until early or mid may,and are normally gone by mid to end oct.
The only trouble I ever have with bears is every 10 years or so when there is lots and lots of food for them in the fall and they stay active right up to december.They follow the trapline and smash boxes and eat bait and catches.Almost always the wrecked boxes are mink boxes on the ground(fish bait)They dont seem to bother the elevated boxes but they will take a hanging catch.